Photographic material and method of producing same



Patented Feb. 16, 1943 PHOTOGRAPH! MATERIAL AND METHOD OF PRODUCING SAME Roelof Jan Hendrik Alink, Jan Hendrik de Boer, Klaas Hinderikus Klaassens, and Cornelis Frederik Veenemans, Eindhoven, Netherlands, assignors, by mesne assignments, to Hartford Trust Company, Hartford,

National Bank and Conn, as trustee No Drawing.

Serial No. 758,334. ary 19, 1934 Application December 19, 1934,

In the Netherlands Jann- 2 Claims. (Cl. 95-6) The present invention relates to photographic material and to the method of producing same, and more particularly to photographic material which has the property of self-coloring.

It is known to manufacture light-sensitive layers by providing a carrier with a diazonium compound and an azo-component, together with substances having an acid reaction and serving as inhibitive agents to prevent untimely coupling.

Furthermore, it has been proposed to combine in a carrier, diazonim compounds with phenol derivatives which are non-coupling per se, but which under the action of an alkali, form a coupling phenol.

In both cases the development of the image is effected by the addition of an alkali, after the exposure has taken place.

Also a method has been suggested in which a paper carrier is soaked in a solution comprising, for instance, a diazonium compound and an azocomponent, and the so-treated carrier is subsequently subjected to intensive drying to give it a sufiicient stability, which stability is further increased by adding to the carrier, substances having an acid reaction. Also this layer after being exposed is developed with an alkali.

We have found that it is possible to produce light-sensitive layers having self-coloring properties by means of a diazonium compound and a dyestufi component, by insuring that a degree of dryness at which no appreciable formation of dyestuif occurs prevails during and after the diazonium compound, the dyestufi-component and the carrier are brought together.

The term self-coloring property as used herein, is to be understood to mean, the property of a light-sensitive material which enables development of the image to be effected after the exposure merely by the action of water vapor or steam, and whereby an intensive color formation takes place on the unexposed portions and little or no color formation takes place at the strongly exposed portions, and fixation of the image is achieved without the subsequent addition or removal of any substance. The speed of such self-coloring" can be increased by moderate heating.

iii

The term dyestuffcomponent as used here-' can either couple with the diazonium compound to form a so-called azo-dyestufl, or can be oxidized by a diazonium compound to form a colored compound. The dyestuir component may be provided as such in or on the carrier, or may be formed there from another compound, for instance by the photo-chemical decomposition of a diazonium compound.

As examples of diazonium compounds may be mentioned, diazonium salts, so-called diazo-oxides, internal diazonium salts, diazo-sulphonates, or the group of substances which have often been classified as diazo anhydrides.

Very favorable results can be obtained in accordance with a. particular embodiment of the invention in which one of the constituents required for the formation of the dyestuff is provided in a state other than its dissolved state.

When carrying out the invention, such combinations of a diazonium compound and of a dyestuif-component may be selected which have such a speed of dyestufi formation that the lightsensitive layer becomes, without further means, self-coloring.

In other combinations in which the speed of dyestufi formation, even in the presence of sufficient water, is comparatively low, it may be advantageous to impart to the layer during its preparation a certain alkalinity in order to obtain a sufliclently high speed of dyestuii formation. However, to minimize the subsequent yellowing of the finished prints, such light-sensitive layers are preferred which have no, or only a slight, alkalinity.

According to one embodiment of the invention a carrier, for instance paper, is impregnated with a solution of a diazonium compound, whereupon it is dried and subsequently rubbed in with powdery dyestuif-component. If desired, the powder may be mixed with a suitable amount of a material causing an alkaline reaction.

It is also possible to treat the layer, after it has been impregnated with a diazonium compounT and subsequently dried, with a non-aqueous solution of a dyestuflE-component, whereupon the solvent is rapidly vaporized. If desired, a fine powder of a material causing alkaline reaction may subsequently also be applied in this case.

Furthermore, a carrier may be provided with a powdery diazonium compound and a powdery dyestufi-component, which are either applied separately or in a mixed condition.

Also, in accordance with the invention, a lightsensitive layer may be obtained by treating the carrier with a non-aqueous solution of a diazonium compound and of a dyestuff-component. either individually or with a mixture of the two; provision being made for a rapid evaporation of the solvent.

After the sensitized layers are prepared according to the invention, they are preferably stored prior to their use in an airtight and dry space, as otherwise prolonged exposure to atmosphere may cause some formation of dyestui! due to the action of the water vapor present in the atmosphere.

When a combination of a diazonium compound and a dyestuiI-component having a very high speed of dyestuif formation is used, it is advisable to carry out the method according to the invention with a very low water content For this purpose the carrier may be previously dried, for instance, by means of an intensively dried air, which may be obtained by drying air for an extended time interval by means of phosphorus pentoxide or by freezing the moisture out of the air.

When using combinations which readily oxidize in the air, it may be advantageous to provide the light-sensitive layer with anti-oxidizing agents.

By developing and fixing the image through the action of water vapor or steam, images exhibiting very sharp contrasts can be obtained, as in this case contact of the layer with a liquid does not occur and "bleeding of the image is prevented. When it is desired to effect the development with water (in its liquid state), it is advisable to provide an extremely thin layer of water in order to minimize "bleeding.

In the case that the dyestuif-component is obtained through the photochemical decomposition of a part of the diazonium compound already present in the carrier, the light-decomposition products thus formed often have a much higher speed of forming a colored compound with a diazonium compound than does the hydroxy compound corresponding to this diazonium compound, and which hydroxy compound may be formed by hydrolysis and subsequent evolution of nitrogen by thermal means from the diazonium compound. In the presence of a large amount of water vapor the light decomposition products lose their high activity and form coloring matter with the diazonium compound, and at about the same speed as does the hydroxycompound. We have found that the higher ac-'- tivity, i. e., speed of color formation of the light decomposition products, can be stabilized by preserving the carrier containing these decomposition products in an atmosphere having a sufficiently high degree of dryness.

In a particular embodiment of the invention, a carrier provided with a diazonium compound is intensively dried until the required degree of dryness has been attained, and then exposed in such a manner that part of the diazonium compound present is photochemically decomposed. The sensitized material thus obtained, when stored in a condition and in a space having the required degree of dryness, gives no formation of dyestuff and the abovementioned characteristic high activity of the light-decomposition product formed is stabilized. If this sensitized material were brought, after a preliminary exposure used for the formation of light decomposition product, into an atmosphere having a suillciently high water vapour content, the dyestuff would immediately be formed, whereby the sensitized material would be spoiled. Consequently the sensitized material should be exposed to the action of water vapor only after a second exposure to light, which exposure serves for the formation of the image.

The preliminary exposure, by means of which the light-decomposition product is formed evenly in the sensitized layer, should preferably decompose such a quantity of the total amount of the diazonium compound that the light-decomposition product and the non-decomposed diazonium compound will yield a maximum formation of dyestufi.

The extent of such preliminary exposure can be experimentally determined by plotting a blackening (coloring) curve corresponding to diflerent exposure times and/0r intensities of the layer comprising a diazonium compound, and determining therefrom those conditions of the preliminary exposure which yield the strongest blackening.

The invention will be more clearly understood by reference to a few examples:

Example I Paper is coated with a. 1% solution of the zincchloride double salt of p-diphenylaminodiazoniumchloride. whereupon it is dried in air and is subsequently rubbed with a very fine powder consisting of 0.5 gram of R-salt (sodium salt of 2 hydroxy naphthalene 3.6-disulphonic acid) and 0.175 gram of anhydrous sodium carbonate, The sensitized material thus obtained gives after exposure and subsequent treatment with steam, a positive image having a dark violet color.

When using, instead of the above-mentioned R-salt-sodium carbonate mixture, a very flne powder consisting of 0.5 gram of phloroglucin and 0.210 gram of sodium bicarbonate, the shade of the positive image becomes dark brown black. The resulting dyestufl is very durable.

Example 11 Paper is treated with a 1% solution of the zincchloride double salt of p-diphenylaminodiazoniumchlorlde, whereupon it is dried in air and subsequently dusted with a very fine powder of phloroglucin. After exposure under a tracing. treatment at room temperature in an atmosphere of water vapor gives, after a few hours, a finished violet black positive image. By using warm water vapor the image forms in about minute.

By replacing the phloroglucin with the naphthol sulfonic acid (2,6), commonly known as Schaflers acid, a brown violet positive image is produced. If desired the papers can be coated with an alcoholic solution of the naphthol sulfonic acid (2,6).

Example III Paper is coated with a 1% solution of the zinc chloride double-salt of p-diphenylumchlorlde, whereupon it is dried in air, and subsequently rubbed with a powder consisting of a-naphthol.

After exposing this material under a tracing, a brown black colored positive image can be immediately produced by treatment with water vapor having a temperature oi about C., and the finished print is thereby obtained.

Example IV Paper is coated with a 1% solution of l-diazonium-2-hydroxy-naphthalene-4-sulphonic acid, whereupon it is air-dried and then a homogeneously mixed fine powder consisting of equal parts of resorcin and anhydrous sodium carbonate is rubbed on the sensitized side of the paper. After exposing the material under a tracing and subsequently bringing it into an atmosphere containing water vapor, a reddish purple image is obtained giving a finished print.

Example V Paper is soaked with a 2% alcoholic solution of naphthol, whereupon 'it is dried in the air, and subsequently painted with a powder of the zinc chloride double salt of p.diphenylaminodiazoniumchloride. After exposure under a tracing for 3 minutes, followed by a treatment of short duration with a very thin layer of water or with steam, a black brown positive image results.

Example VI Paper is rubbed with a fine powder consisting of 1.00 gram of zinc chloride double salt of p-diphenylaminodiazoniumchloride and 0.30 gram of phloroglucin. After exposure under a tracing and treatment with hot water vapor a greenish black positive image results.

Example VII Paper is treated on one side with a 2% solution of 2-diazonium-l-hydroxybenzene 4 sulphonic acid and 5.3% of Cu(NO3)26I-I2O in water and subsequently very intensively dried by means of a current of gas free from water vapor. In this state the material is subjected to a preliminary exposure for 5 seconds and at a distance of 25 centimeters to the light of a 5 kw. incandescent lamp or for a corresponding time to the light of a mercury discharge tube. When using the paper a blue positive image is immediately formed after the sensitized material thus obtained, has been exposed under a tracing for about 2 minutes at a distance of 25 centimeters from a- 5 kw. incandescent lamp and has been treated with warm water vapor.

Example VIII Paper is treated with a 1.9% solution of a 2-di azonium-lhydroxy 5 methylbenezne 4 sulphonic acid and 5% CU.(NO3)26H2O in water and is subsequently treated in accordance with Exampie VII.

0n using it a blue positive image results, after exposure under a tracing followed by ironing the paper under a damp cloth with a warm smoothing iron for about minute.

Example IX Paper is treated with a 2% aqueous solution of 2-diazonium-l-hydroxybenzene 4 sulphonic acid and 5.3% Cu(NOa)26H2O and is then dried in a current of gas free from water vapor. In this condition the material is exposed till the diazonium compound is entirely copied out. Thereupon the so-treated paper is rubbed, in a practically perfectly dry atmosphere, with a fine powder of 1-hydroxy-5-methyl-2-diazoniumbenzene-4-sulphonic acid. After exposure under a tracing and subsequent treatment with water vapor, a steel blue positive image results.

Example X Paper is soaked with a 2% solution of e-naphthalene diazoniumchloride, is dried, and is subsequently exposed to light, due to which the diazonium compound is completely copied out.

Thereupon the layer is covered with a powder of p diphenylaminodiazoniumchloride. After being exposed under a tracing, followed by treatment with steam, a black brown positive image results.

While we have described our invention in connection with specific examples, we do not wish to be limited to same, but desire the appended claims to be construed as broadly as permissible in view of the prior art.

What we claim is:

1. In the method of producing from a diazonium compound component and a dyestuff-component capable of forming a dyestuif in the presence of moisture a light-sensitive layer of the type in which image development is effected after exposure merely by the action of moisture and without the removal or addition of any chemical substance, the steps of applying a solution of a diazonium compound to a carrier, drying the carrier, exposing the carrier to photochemically decompose the diazonium compound and to form evenly over the surface of the carrier the dyestuff-component, applying the diazonium compound component in its powdery form to the carrier, and maintaining during and subsequent to the application of the diazonium component a degree of dryness suflicient to prevent appreciable formation of dyestufi.

2. In the method of producing photographic images, the process which comprises, applying to a carrier a diazonium compound, drying the carrier, photochemically decomposing the diazonium compound to form a dyestufi component, apply- .ing to the so-treated carrier a powdery diazonium compound component capable of reacting with said dyestufi component in the presence of moisture to form a dyestuff, maintaining during the application of the diazonium component and subsequent thereto a degree of dryness suflicient to 

